1. Field of the Invention
The present general inventive concept relates to an ink circulation apparatus and an inkjet printer including the same, and more particularly, to an ink circulation apparatus which does not discharge ink during an ink circulation process and has an efficient ink circulation flow route, and an inkjet printer including the same.
2. Description of the Related Art
Generally, an inkjet printer deposits ink on a printing paper through nozzles provided in a head to form a predetermined image on the printing paper. However, in the case that the nozzles are blocked by foreign substances, such as, minute dust or bubbles, an image cannot be formed on a part of the printing paper corresponding to the blocked nozzles. Thus, a filter is generally provided on an ink flow route between an ink tank which stores ink and the nozzles to filter the bubbles and/or the foreign substances.
In the case of an ink jet printer having a difficulty in replacing a head because the head is fixed on a printer housing, there is a need for an ink circulation process for recovering bubbles and foreign substances from the ink flow route between the nozzles and the ink tank into the ink tank so as to prevent the nozzles from being blocked.
As illustrated with a solid line arrow 40 in FIG. 1, a conventional inkjet printer 1 has an ink circulation process in which the ink is circulated via an ink tank 10, a negative pressure part 50, a head assembly 20, and a circulation pump 30 in sequence by an operation of the circulation pump 30. The negative pressure part 50 applies a negative pressure to the head assembly 20 to prevent the ink from being discharged through nozzles of the head assembly 20 during the ink circulation process. Here, the filter (not illustrated) is positioned on the ink circulation flow route inside the negative pressure part 50 to filter the foreign substances.
In the conventional inkjet printer 1, the filter is positioned on the ink circulation flow route, so that the circulation pump 30 should have a large capacity to overcome a flow resistance owing to the filter.
Further, the conventional inkjet printer 1 is inefficient because it circulates the ink through all the head assembly 20, the negative pressure part 50, and the filter. Because the foreign substances and the bubbles in the head assembly 20 ahead of the filter are filtered by the filter, the head assembly 20 contains relatively clean ink having less foreign substances and less bubbles in comparison with the ink in other areas.
Also, an ink circulation process by a positive pressure pump has been disclosed in Japanese First Patent Publication No. 2004-351641, which is designed to minimize the amount of ink wastefully discharged through the nozzles in an ink circulation process.